Genome sequencing and data collection has advanced rapidly in the last 25 years

Comparative studies of genomes

Advance our understanding of the evolutionary history of life

Help explain how the evolution of development leads to morphological diversity

79Comparing Genomes

Genome comparisons of closely related species help us understand recent evolutionary events

Genome comparisons of distantly related species help us understand ancient evolutionary events

Relationships among species can be represented by a tree-shaped diagram

80Figure 21.16BacteriaMost recentcommonancestorof all livingthingsEukaryaArchaea43201Billions of years agoChimpanzeeHumanMouse400102030506070Millions of years ago 81Comparing Distantly Related Species

Highly conserved genes have changed very little over time

These help clarify relationships among species that diverged from each other long ago

Bacteria, archaea, and eukaryotes diverged from each other between 2 and 4 billion years ago

Highly conserved genes can be studied in one model organism, and the results applied to other organisms

82Comparing Closely Related Species

Genetic differences between closely related species can be correlated with phenotypic differences

For example, genetic comparison of several mammals with nonmammals helps identify what it takes to make a mammal

83

Human and chimpanzee genomes differ by 1.2, at single base-pairs, and by 2.7 because of insertions and deletions

Several genes are evolving faster in humans than chimpanzees

These include genes involved in defense against malaria and tuberculosis, regulation of brain size, and genes that code for transcription factors

84

Humans and chimpanzees differ in the expression of the FOXP2 gene, whose product turns on genes involved in vocalization

Differences in the FOXP2 gene may explain why humans but not chimpanzees communicate by speech

85Figure 21.17EXPERIMENTHeterozygote onecopy of FOXP2disruptedHomozygote bothcopies of FOXP2disruptedWild type two normal copies of FOXP2Experiment 1 Researchers cut thin sections of brain and stainedthem with reagents that allow visualization of brain anatomy in aUV fluorescence microscope.Experiment 2 Researchers separatedeach newborn pup from its motherand recorded the number ofultrasonic whistles produced by thepup.RESULTSExperiment 1Experiment 2400300Number of whistles200100(Nowhistles)Wild typeHeterozygoteHomozygote0WildtypeHetero-zygoteHomo-zygote 86Figure 21.17aEXPERIMENTHeterozygote onecopy of FOXP2disruptedHomozygote bothcopies of FOXP2disruptedWild type two normal copies of FOXP2Experiment 1 Researchers cut thin sections of brain and stainedthem with reagents that allow visualization of brain anatomy in aUV fluorescence microscope.RESULTSExperiment 1HomozygoteWild typeHeterozygote 87Figure 21.17bEXPERIMENTHeterozygote onecopy of FOXP2disruptedHomozygote bothcopies of FOXP2disruptedWild type two normal copies of FOXP2Experiment 2 Researchers separated each newborn pup from its motherand recorded the number of ultrasonic whistles produced by the pup.RESULTSExperiment 2400300Number of whistles200100(Nowhistles)0Hetero-zygoteHomo-zygoteWildtype 88Figure 21.17cWild type 89Figure 21.17dHeterozygote 90Figure 21.17eHomozygote 91Figure 21.17f 92Comparing Genomes Within a Species

As a species, humans have only been around about 200,000 years and have low within-species genetic variation

Variation within humans is due to single nucleotide polymorphisms, inversions, deletions, and duplications

Most surprising is the large number of copy-number variants

These variations are useful for studying human evolution and human health

93Comparing Developmental Processes

Evolutionary developmental biology, or evo-devo, is the study of the evolution of developmental processes in multicellular organisms

Genomic information shows that minor differences in gene sequence or regulation can result in striking differences in form

94Widespread Conservation of Developmental Genes Among Animals

Molecular analysis of the homeotic genes in Drosophila has shown that they all include a sequence called a homeobox

An identical or very similar nucleotide sequence has been discovered in the homeotic genes of both vertebrates and invertebrates

Homeobox genes code for a domain that allows a protein to bind to DNA and to function as a transcription regulator

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